To investigate the relationship between farming exposures and asthma, allergies and related phenotypes, we carried out a nested case control study of asthma within a large cohort of farmers -- the Agricultural Health Study. This study follows up findings regarding the association between correlates of microbial exposures and various questionnaire-based asthma and atopy phenotypes. It was also designed to follow-up findings based on questionnaire data of positive associations between pesticide exposures and questionnaire-based asthma phenotypes. To confirm and better understand these associations, objective measures of asthma and atopy phenotypes were made along with more detailed exposure assessment. This study builds upon the Agricultural Health Study, a large cohort of farmers and their spouses in Iowa and North Carolina. We identified presumptive cases of asthma and non cases from the third phase of cohort follow-up and made home visits on eligible subjects. The Lung Health Study was launched on Feb 4, 2009. Field work ended September 30, 2013 and telephone interviews ended on November 15, 2013. We completed home visits on over 3,200 individuals. Pulmonary function was measure at home visit along with exhaled nitric oxide and blood was analyzed for immunoglobulin E (IgE) to a panel of 10 common allergens. Endotoxin was measured in house dust on over 2500 subjects. The house dust microbiome was measured on a random sample of 1000 individuals. Genome wide single nucleotide polymorphism data and genome methylation data were generated.